<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>

	<body>

	</body>
	<script type="text/javascript">
		var arr = {
			name: "2000",
			age: 1000
		}

		function getkey() {
			var result = ""
			for(var i in arr) {
				if(arr[i] == 1000) {
					result = i
				}
			}
			return result
		}
		console.log(getkey())
	</script>

</html>